Influence of biopolymers, iron, biofouling and Asellus aquaticus on Aeromonas regrowth in three non-chlorinated drinking water distribution systems

In three separate distribution systems supplied with non-chlorinated drinking water produced from the same surface water, but with different microbial regrowth conditions, the spatiotemporal variation of biological stability and biofouling (biofilm and loose deposits) was determined. Main objective was to establish the cause(s) for differences in regrowth and to elucidate the mechanism of the observed differences in Aeromonas regrowth. Enhanced HPC22 and Aeromonas regrowth in two of these drinking water distribution systems (DWDSs) was related to (i) higher biopolymer concentration in the drinking water, (ii) increased biofouling with non-dissolved organic carbon and iron and (iii) the presence of Asellus aquaticus biomass in the loose deposits. The biofouling parameter iron accumulation rate was a good predictor for biofouling conditions in the biofilm and loose deposits. The observed association of A. aquaticus biomass in the loose deposits with Aeromonas regrowth in the drinking water suggests that release from the A. aquaticus biomass is a major mechanism for this regrowth. Complex interactions between biopolymers, iron and A. aquaticus as cause for the undesired regrowth needs further studies where the efficacy is assessed of biopolymer and Fe reduction and/or of removal of loose deposits (incl. A. aquaticus) by pipe flushing in the DWDS to control this regrowth. [Display omitted] •Biopolymers and Fe biofouling promote regrowth in non-chlorinated drinking water.•Invertebrates in the food web of the DWDS are an essential part of the biofouling.•Technical Aeromonas standard potentially indicates the presence of A. aquaticus.•Regrowth control by biopolymers/Fe reduction and pipe flushing needs further study.